The kids of “Rent,” the 1996 Broadway musical about East Village bohemians, have grown up and sold out.

Just as “Rent,” set in the early '90s, reflected pre-Giuliani New York, the new Broadway musical “If/Then” reflects post-Bloomberg New York.

In “Rent,” Mimi, Roger and the gang struggled with drugs and AIDS. But mostly they fought the landlord, and fought selling out to the man.

Looking back, “Rent” looks like a turning point: Soon after, AIDS stopped being a death sentence, and heroin chic stopped being romantically cool.

In retrospect, even Benny, the landlord, seems like an earnest entrepreneur who has invested in a building and is trying to keep it up. Yet he must deal with tenants who aren't sick or addicted — but just think the world owes them a living.

What happened next? Well, “If/Then” — which stars two of the same headliners as “Rent” — is a jarringly accurate sequel, nearly two decades later.

New York is no longer a place where free-spirited kids go because it's so cheap and disorderly that you can live here without doing something you don't feel like doing in order to pay the rent.

It's a place responsible adults go despite the fact that it's so expensive — because New York is where smart, ambitious, organized people want to be.

The play centers on Elizabeth, “flirting with 40,” who returns to New York after 12 years in Phoenix. “No more wasted time,” she vows.

An urban-planning Ph.D., Liz wants to work for the city. Somewhat implausibly (hey, that's show biz), she's sitting in Madison Square Park when the city's planning chief, Stephen, calls her and offers her the job of deputy director.

“You cannot take a job with the city,” insists Liz's old New York friend Lucas. “Aren't you a little young to be selling out?”

But Lucas, a professional protester, is not the hero of this tale. The audience sees him as an affable loser. “Are you a mime?” asks a young acquaintance when Liz introduces Lucas as a “street activist.”

Her City Hall portfolio is to rezone the Far West Side, allowing for dense residential development in return for some affordable-housing set-asides by builders. “The map of the city will be redrawn whether you like it or not,” she rather pragmatically informs Lucas.

“We can rezone 1,000 city blocks,” the characters sing. “We can draw a brand-new grid…On the West Side, a railyard is reclaimed.”

Liz finds her boss, Stephen, attractive in part because he croons of Penn Station, “the old one goes, the Garden goes” (yeah, this is no “Cats,” but it's doing well enough at the box office).

Eventually, Liz co-ops even Lucas. When her colleagues ask her why she invited his group to the groundbreaking, she notes that accepting the invitation meant Lucas would “lose his outsider status…They won't picket their own ceremony.” Bloom­berg's staffers should be proud.

“If/Then” even promotes Bloom­berg-style street redesign. Via dream-sequence-style fantasy, the storyline splits Elizabeth into two characters — the one who goes for the planning job, and one who goes for a less stressful academic job.

Academic Elizabeth, heavily pregnant, picks up a newspaper and weeps. “A child was killed in traffic,” she sobs, because she had made the wrong choice: “The idiot in charge of city planning…wanted the cars” going to the new Far West Side development “to move smoothly like a highway.”

And notably missing from the play are the crime and disorder that plagued “Rent”-era New York. The characters wheel their urban babies to the park with no hint of fear.

But also missing is something more worrisome: the private sector. Liz's best friend Kate is a public-school teacher; another character is an ER doctor (whose business is mostly car crashes).

Here, the 20-somethings who come to the city want to work for the city.

The private sector is missing in another way, too: The implication is that the brilliant people who work for the city figure everything out, in a Barclays Center central-planning way. No visionary for-profit entrepreneurs necessary.

When Liz says she's “mothered” dozens of buildings, it's weird not only because buildings aren't babies, but also because the city shouldn't be that all-powerful.

Mostly, though, “If/Then” shows New York as it is: a place where people come to thrive rather than succumb to nihilism (and where people who truly need help can get it).

But this may be reason for audience members to shiver. After all, today “Rent” looks like a relic of the past.